package com.fishing.util.personal;

import java.util.HashMap;

public class MyHashMap extends HashMap{
    @Override
    public Object put(Object key,Object value) {
    	//如果已经存在key,不覆盖原有key对应的value
    	if(!this.containsKey(key))
    		return super.put(key, value);
    	return null;
    }
}
